This invention relates to a method for manufacturing needle attached sutures and an apparatus therefor, in which the end of a needle used for surgical operations and the like is swaged in a state that the lead end of a suture is inserted in an insertion hole formed in the end of the needle to combine the suture with the needle.
Recently, in the field of medical industry, there have been marketed sterilized needle attached sutures for surgical operations in which the lead end of a suture is fixedly attached to a needle. Such needle attached suture can be produced by retaining a needle in a certain orientation, and swaging the end of the needle after inserting the lead end of a suture in an insertion hole formed in the end of the needle (as disclosed in, e.g., Japanese Examined Patent Publication No. HEI 4-66579).
To produce such needle attached suture, it is required to cut a suture at a predetermined target value to obtain a suture strand of the predetermined length. Conventionally, there have been known the following methods for setting the length of the suture strand at a desired value:
A) A suture is cut into suture strands of a certain target length in advance, and then each suture strand is attached to a needle; and
B) A suture wound around a bobbin or its equivalent is also wound around a brake roller mounted in a specified position along the suture feed direction. A rotational amount of the brake roller is monitored by a rotary encoder in such a manner that the brake roller stops its rotation to suspend feeding of the suture when it is confirmed that the rotational amount of the brake roller reaches a predetermined value corresponding to the target length of the suture to be cut after feeding of the suture is initiated. Upon the brake roller halting the feeding of the suture, the suture is cut at a certain position (see Japanese Examined Patent Publication No. HEI 5-11981).
In the method A), it is required to separately perform the step of cutting the suture to obtain a suture strand of the certain length and the step of combining the suture strand with a needle. In other words, the cutting step and the bonding step cannot be executed sequentially, thus resulting in a hindrance to raise production efficiency and to pursue mass production.
The method B) has involved another problem. Specifically, it is likely that the suture fed forward slips over the brake roller, resulting in a detection error of the rotary encoder which detects the feed amount of the suture. Accordingly, it is difficult to cut the suture at a desired position accurately. Furthermore, the above slippage is liable to occur as the feed speed of the suture is increased. This remarkably restricts the suture feed speed, resulting in a prolonged cycle time and lowers production efficiency.
Moreover, in the case where the target value of the suture strand is to be altered, the following steps are required. Specifically, the altered amount of feeding the suture is converted to a rotational amount detected by the rotary encoder, and a whole program for controlling the brake roller is required to be changed based on the rotational amount of the rotary encoder after conversion. In other words, this method is not feasible in quickly responding to the alteration of the target length of a suture strand.
In view of the above, an object of this invention is directed to a method and an apparatus for manufacturing needle attached sutures accurately with the same desired length, with a simple construction and high efficiency.